Step-by-step explanation:
a)
[tex] \frac{1 + \sin y}{ \cos y} + \frac{ \cos y}{1 + \sin y} = \frac{1 + 2 \sin y + \sin^{2} y + \cos ^{2} y}{ \cos y(1 + \sin y)} [/tex]
[tex] = \frac{2 + 2 \sin y}{ \cos y (1+ \sin y)} = \frac{2}{ \cos y} = 2 \sec y[/tex]
b)
[tex] \frac{ \cot x}{ \tan x + \cot x} = \frac{ \cos x}{ \sin x( \frac{ \sin x}{ \cos x} + \frac{ \cos x}{ \sin x} )} [/tex]
[tex] = \frac{ \cos x}{ \frac{ \sin^{2} }{ \cos x} + \cos x } = \frac{ \cos x}{ \frac{ \sin ^{2} x + \cos^{2} x}{ \cos x} } [/tex]
[tex] = \cos ^{2} x[/tex]
c) Note that cscx = 1/sinx so
[tex] \csc^{2} \theta \tan^{2} \theta - 1= \frac{1}{ \cos^{2} \theta } - 1[/tex]
[tex] = \frac{1 - \cos^{2} \theta }{ \cos \theta} = \frac{ \sin^{2} \theta}{ \cos ^{2} \theta } = \tan^{2} \theta[/tex]
